University of Cambridge Natural Radiocarbon Measurements X

Abstract

Measurements reported in this paper were obtained in the Cambridge Radiocarbon Dating Laboratory during 1970–71. For most determinations, pure carbon dioxide at a pressure of 2 atm was used to fill the copper proportional counters, of 0.5 L or 1.5 L volume. The counters were protected by a massive lead shield and a plastic scintillation anticoincidence screen (Switsur, Hall, and West, 1970). Modern sample gas was obtained from the 1845 to 1855 growth rings of a locally grown oak tree which was felled in 1950. Background was prepared from Welsh anthracite. The contemporary standard is compared frequently with the activity of the International NBS oxalic acid standard. Sample ages are calculated using the conventional half-life of 5568 ± 30 years and the uncertainty stated in terms of one standard deviation of the counting statistics.